mmc: meson-gx: remove unused members irq, ocr_mask from struct meson_host

Member ocr_mask is never used and member irq we can replace with a
local variable in meson_mmc_probe. So let's remove both members.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Kevin Hilman <khilman@baylibre.com>
Tested-by: Kevin Hilman <khilman@baylibre.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>